Conventionally, in the automatic xerographic process, a latent electrostatic image of an original to be reproduced is recorded upon an image retaining member and the image then made visible, or developed, by means of a finely divided particulate toner material. In reusable xerography, the developed toner image is generally transferred from the image retaining member to a copy sheet, such as paper or the like, and the image affixed thereto to form a permanent record of the original input scene information. Although a preponderance of the toner material comprising the developed image is transferred to the copy sheet, a small amount of residual toner is nevertheless invariably left behind on the image retaining member after the transfer operation. In order to restore the image retaining member to conditions suitable for reuse, this vestige of toner must be cleaned or removed from the surface thereof before a new imaging cycle is instituted.
The cleaning of the image retaining member may be accomplished in a number of different ways. One prevalent technique is to separate the residual toner from the image retaining member by means of an elastomeric blade element as disclosed in U.S. Pat. No. 3,660,863 to Gerbasi. In the blade cleaning process, the cutting edge of the blade is arranged to move between the residual toner particles and the image bearing surface to chisel or cut the toner particles therefrom. Generally, the residual toner is collected in a chamber where it may either be stored for later disposal or recirculated for further use. In operation the chamber and entrance thereto have to be open to receive the residual toner but in such a way that the toner is confined within the chamber and so cannot escape or migrate to other parts of the xerographic machine. In practice, the chamber is usually provided closely adjacent the image retaining member and in such a manner as to form a sealed enclosure with the image retaining member itself being disposed in a sealing relationship with the chamber or chamber housing. For example, U.S. Pat. No. 3,838,472 discloses a xerographic copier with a blade cleaning arrangement in which the image retaining member is a photoconductive drum disposed such that a portion of its circumference is seated in the opening of the collecting chamber thereby covering and closing it. In that case sealing is enhanced by the inclusion below the cleaning blade of a cylindrical sealing roll arranged to ride in light biasing contact with the drum surface. It is noted that in order to reduce localized wear on the blade's cutting edge and also to prevent entrapment of foreign matter between the blade and the drum surface, the blade can be stepped longitudinally in predetermined increments back and forth across the drum surface over a path travel substantially normal to the direction of motion of the drum. However, although the blade is movable in this manner, it always remains in contact with the drum surface and does not perform any part in closing or sealing the toner collecting chamber.
In U.S. Pat. No. 4,158,498 there is disclosed a blade cleaning system in which the blade is arranged for movement between a first position in which the blade operatively engages the image retaining member to remove the residual toner therefrom and a second position at which the blade is spaced apart from the image retaining member so that the blade itself can be cleaned by a special cleaning mechanism.
Published PCT application No. WO/85 04733 discloses a cleaning apparatus for a color copier having several chambers fixed within the main assembly of the copier for collecting different color toners respectively. A respective cleaner blade is fastened to each chamber at the entrance thereto. In a first position the blades engage the photoreceptor to scrape off a respective color toner which is collected in the associated open chamber. By pivoting an entire chamber about its longitudinal axis the associated blade fixed thereto is moved to a position where it assists in closing off the chamber from receiving airborne toner particles of a color not intended to be collected. It is emphasized that in this case the cleaner blades merely assist in preventing undesired airborne toner particles from entering a particular chamber and as described they do not seal the chambers in such a manner as to prevent toner contained therein from escaping.
Recently there has been a move towards including the photoreceptor together with other process means such as a charge corotron, a development device, a transfer corotron, and especially a cleaning device in a single cassette. Examples of such cassettes are described in U.S. Pat. No. 3,985,436, Japanese Patent No. 60-11868, and Japanese Patent No. 59-53859, all of which show various combinations of process elements in a single cassette. The use of a cassette of this kind enables the easy replacement of those parts of the xerographic machine which are most likely to deteriorate with use, especially the photoreceptor, but also the development and cleaning systems as well as the corotron wires. A further advantage of containing the major xerographic process elements within a cassette is that interchangeable cassettes may be used in a given copying machine to provide different development characteristics or different colored development. U.S. Pat. No. 3,966,316 discloses a cassette incorporating both the copying drum and a brush type cleaning unit for an imaging system. Japanese Patent No. 58-82285 shows a process unit containing toner supplies to prevent toner from dispersing when the process unit is removed, and including a cleaning blade which is brought into contact with photoreceptor, only when the cassette is in position in the image forming device.
Our co-pending U.S. application Ser. No. 38,093, filed Apr. 14, 1987, which along with the other patents and publications cited herein, is incorporated by reference, concerns a process unit comprising such a xerographic process cassette in which the image retaining member is loosely retained in the process unit when the process unit is removed from the main assembly of the xerographic machine, and is adapted to be supported in an operative position by support means forming part of the main assembly when the process unit is inserted into the main assembly. This arrangement has the advantage of making the insertion and withdrawal operations simple and reliable, without the need for elaborate mechanisms to ensure that the photoreceptor arrives at exactly the correct position for an in-focus image to be formed on it by the optical system of the xerographic machine. However, when the photoreceptor is loosely retained it can no longer effectively close and seal the residual toner collecting chamber. Without the chamber being sealed the toner is able to escape into the cassette and contaminate other components in the unit particularly when the cassette is being handled outside the main assembly when it will obviously be subject to significant disturbance.
According to a first aspect of the present invention there is provided apparatus for separating residual toner material from the surface of a reusable image retaining member of a reproducing machine, comprising blade means arranged for movement between two positions wherein at the first position the blade means operatively engages the image retaining member to remove said residual toner material therefrom and that the second position the blade means is spaced apart from the image retaining member, and a generally enclosed chamber with an opening for collecting the residual toner material as it is removed by said blade means, characterized in that in said second position the blade means covers the opening and closes the chamber in such a manner as to form a sealed enclosure to prevent the toner material contained therein from escaping.
The apparatus in accordance with the invention has the advantage that the toner can be sealed in the collecting chamber by the cleaner blade alone, obviating any reliance on the photoreceptor to perform a sealing function. Hence this cleaning apparatus is ideally suited for incorporation in a process unit of the kind hereinbefore discussed wherein the photoreceptor is only loosely retained in the cassette outside the main assembly. Preferably, the blade means is moved automatically from the second sealing position to the first cleaning position when the process unit is inserted into the working position in the main assembly, and automatically moved back to the sealing position when the process unit is withdrawn.